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✅Biology AS Unit 2 > 🔺🔥2.2 Adaptations For Gas Exchange > Flashcards

🔺🔥2.2 Adaptations For Gas Exchange Flashcards

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1
Q

What is a respiratory surface

A

The site of gas exchange e.g respiratory surface of a fish = gills and human = alveoli in the lungs

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2
Q

What is gas exchange

A

The diffusion of gases down a concentration gradient across a respiratory surface, between an organism and it’s environment

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3
Q

What is the respiratory surface in leaves

A

Spongy mesophyll cells in leaves

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4
Q

What is the respiratory surface in insects

A

The tracheae

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5
Q

What must a respiratory surface have/be for efficient gas exchange

A
  • large surface area to volume ratio
  • thin so diffusion pathway is short
  • permeable do that respiratory gases diffuse easily
  • mechanism to produce a steep diffusion gradient across surface by bringing oxygen/removing co2 rapidly
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6
Q

Give an example of a unicellular organism

A

Amoeba

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7
Q

Why can unicellular organisms complete only simple diffusion

A

Because:

  • large surface area:volume ratio
  • cell membrane is thin so diffusion into cell is rapid
  • a single cell is thin :: diffusion distance inside cell is short
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8
Q

Why is unicellular organisms being thin/large surface area beneficial

A
  • can absorb enough oxygen across cell membrane to meet respiratory demands
  • can remove Co2 fast to prevent building up a high concentration and making cytoplasm too acidic for enzymes to function
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9
Q

Why are multicellular organisms less efficient for gas exchange?

A

Lower surface area to volume ration so simple diffusion across cell membrane does not meet demands

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10
Q

Name an organism that has overcome the problem of their size to diffuse gas simply

A

Flatworms because they have a large surface area to volume ratio :: no part of the body is far from the surface to diffusion paths are short

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11
Q

Which is more efficient for gas exchange, a spherical or cylindrical organism

A

Cylindrical organism as it has a larger surface area to volume ratio

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12
Q

Define metabolic rate

A

The rate of energy expenditure by the body

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13
Q

Define terrestrial organism

A

An organism that lives on land e.g earthworm

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14
Q

Describe the gas exchange in an earthworm compared to flatworm

A

-cylindrical so surface area to volume ratio is smaller than flatworms :: can’t simply diffuse but larger than compact organism of same volume

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15
Q

What is the respiratory surface of earthworm and describe why this is important

A
  • Skin is the respiratory surface, kept moist by secreting mucus
  • need for moist surface restricts earthworm to damp soil environment
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16
Q

What do earthworms contain that flatworms don’t

A

A circulatory system containing haemoglobin which has an affinity for oxygen carrying but around the body and away from surface maintaining diffusion gradient

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17
Q

Why does the earthworm have a low oxygen requirement

A

Because it’s slow moving and has a low metabolic rate

This means oxygen diffuses across skin into the blood capillaries beneath

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18
Q

Name another aspect maintaining concentration gradient in the earthworm

A

Carbon dioxide is carried in the blood and diffuses out across the skin, down concentration gradient

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19
Q

Why do multicellular animals e.g mammals and insects have special features not seen in unicellular organisms

A
  • generally have a higher metabolic rate :: need to deliver more oxygen to respiring cells
  • as size and the specialisation of cells increases tissues and organs become more interdependent
  • must actively maintain concentration gradient across respiratory surface
  • respiratory surfaces must be thin so short diffusion pathway
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20
Q

What problems could arise due to thin respiratory surfaces?

What adaptation protects them?

A

Fragile and could easily be damaged

As they are inside an organism, lungs of a mammal and gills of a fish protect them

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21
Q

How to larger organisms maintain a concentration gradient?

A

Move environmental medium, air or water, and in larger animals the internal medium the blood. (Ventilation mechanisms)

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22
Q

What major problems did terrestrial organisms face when colonising land from the sea?

A
  • water evaporates from body surface resulting in dehydration
  • gas exchange surfaces must be thin and permeable with a large surface area but water molecules are very small and :: pass through gas exchange surfaces meaning surfaces aren’t always moist
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23
Q

How did animals evolve so they could first survive on land

A

Gills could not function on land but the tracheae of insects and the lungs of vertebrates do

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24
Q

How to lungs minimise water loss,

Name 2 simple advantages

A

Lungs are internal, minimising water and heat loss

They allow gas exchange with air and allow animals to be active

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25
Q

Give some examples of amphibians

A

Frogs, roads and newts

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26
Q

Name some facts about the amphibians skin

A
  • Skin is moist and permeable

- Located above a developed capillary network

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27
Q

How does gas exchange occur in amphibians

A

Gas exchange takes place through the skin, and when animal is active, in the lungs also

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28
Q

Name some examples of reptiles

A

Crocodiles, lizards and snakes

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29
Q

Name an an adaptation that reptiles have to improve gaseous exchange

A

Their Lungs have a more complex internal structure than other mammals e.g amphibians and therefore increased surface area for gas exchange

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30
Q

What 3 things so all advance multicellular organisms have for gas exchange

A

1) ventilation mechanism
2) internal transport system e.g circulatory system
3) respiratory pigment (haemoglobin) to increase oxygen carrying capacity

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31
Q

Why is birds having large lungs an advantage?

A

Advantage as large volumes of oxygen can be processed as flight requires a lot of energy (metabolically active)

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32
Q

Describe ventilation method in birds

A
  • don’t have a diaphragm

- ribs and flight muscles ventilate their lungs more efficiently than methods used by other vertebrates

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33
Q

Define ventilation

A

Bringing gases to or from a gas exchange surface; only occurs In some organisms

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34
Q

Name 3 characteristics of all gills

A
  1. One way current of water, kept flowing by specialised ventilation mechanism
  2. Many folds, providing a large surface area over which water flows for gas exchange
  3. Large surface area, maintained as the density of water flowing prevent the gills from collapsing
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35
Q

What are the 2 main groups of fish

What is the main difference between these two groups?

A

Bony and cartilaginous fish

Bony fish have a skeleton of bone, cartilaginous fish have a skeleton of cartilage

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36
Q

Cartilaginous fish:
How many gills do cartilaginous fish have in either side?
What is this arrangement called?
Where are these visible from?

A

Gills in 5 spaces on each side
Arrangement = gill pouches
Visible= open to the outside at gill slits

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37
Q

Cartilaginous fish:

Define parallel flow

A

Blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where it’s concentration in the blood and water is equal (50-50)

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38
Q

Cartilaginous fish:

Why is the ventilation system of Cartilaginous fish less efficient than that of bony fish?

A
  • no special mechanism to force water over gills :: must keep swimming for ventilation to occur
  • blood and water travel In same direction over capillaries (parallel flow) :: blood oxygen concentration is limited to 50% of its max value
  • gas exchange does not occur over whole gill Lamellae
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39
Q

LEARN OXYGEN DIFFUSION IN PARALLEL FLOW DIAGRAM

A

LEARN OXYGEN CONCENTRATION ACROSS THE GILL LAMELLA OF A CARTILAGINOUS FISH DIAGRAM

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40
Q

Bony fish:

What is the operculum

A

The covering over the gills of a bony fish

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41
Q

Bony fish:

Where do bony fish live?

A

Fresh water and Sea water

Most numerous of aquatic vertebrates

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42
Q

Bony fish:
Example of a bony fish?
Describe the structure of the gills in a bony fish

A
  • Catfish

- Internal skeleton made of bone with the operculum covering its gills

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43
Q

Describe the process of ventilation in bony fish (taking water in)

A

A) mouth opens (acts as a pump)
B) operculum closes
C) floor of mouth is lowered
D) volume inside mouth cavity increases
E) pressure inside mouth cavity decreases
F) water flows in as external pressure is higher than pressure inside the mouth

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44
Q

Describe the process of ventilation in a bony fish (forcing water out over the gills)

A

A) mouth closes
B) operculum opens
C) floor of mouth is raised
D) volume inside mouth cavity decreases
E) pressure inside mouth cavity increases
F) water flows our over he gills because the pressure inside the mouth cavity is higher than in the opercular cavity and outside

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45
Q

How many pairs of gills to bony fish have?

What is each gill supported by?

A
  • 4 pairs of gills

- Each gill is supported by a gill arch made of bone

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46
Q

Where are the gas exchange surfaces located in a bony fish?

A

On the gill fillents in a section called the gill lamellae

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47
Q

Why are gill lamellae vital for gas exchange in bony fish?

A

Vital as the gill filaments are held apart by water flowing between them providing a large surface area for gas exchange

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48
Q

Why do fish die out of water?

A

Out of water the gill fillaments stick together and collapse so much less surface area is exposed and not enough gas exchange occurs

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49
Q

Define counter current flow

A

Blood and water flow in opposite directions at the gill lamellae maintaining the concentration gradient and therefore, oxygen diffusion into the blood alone their entire length

50
Q

Name the flow of water through a bony fish until gas exchange

A

Mouth cavity
Opercular cavity
Gill pouches
Flows between gill lamellae where blood in gill capillaries flows in opposite direction (counter-current flow)

51
Q

LEARN COUBTER CURRENT FLOW DIAGRAM

A

LEARN DIAGRAM OF FISH GILLS ETC ON Pg 166

52
Q

Why is counter current flow in bony fish more efficient than parallel flow In cartilaginous fish

A

Water always has a higher oxygen concentration than the blood in counter-current flow so oxygen diffuses into the blood along whole length of gill lamellae, removes about 80% of oxygen from water

53
Q

Why is a high percentage of oxygen extraction (e.g 80% in bony fish) vital to fish?

A

Important to fish as water contains much less oxygen than air

54
Q

LEARN OXYGEN DIFFUSION IN COUNTER-CURRENT FLOW

A

LEARN OXYGEN CONCENTRATION ACROSS THE GILL LAMELLAE OF A BONY FISH DIAGRAM

55
Q

Statement about oxygen concentration across gill lamellae of bony fish

A

With increase distance along the gill lamella, the concentration of oxygen in the blood increase and that of water decreases until the concentration in blood is very high and water is very low

56
Q

Describe the Carbon dioxide diffusion in cartilaginous fish vs bony fish

A

In cartilaginous fish carbon dioxide diffuses from the blood to the water
In a bony fish (due to counter-current system) carbon dioxide diffuses out of the blood along whole length of gill lamellae :: more efficient than the carbon dioxide loss from gills of cartilaginous fish

57
Q

Name the 3 vital things gills provide

A

1-specialised respiratory surface, rather than using body surface
2- large surface extended by gill filaments and gill lamellae
3- an extensive network of blood capillaries, with blood carrying haemoglobin allowing efficient diffusion of oxygen into blood and carbon dioxide out

58
Q

Where are the lungs located in the human breathing system

A

Enclosed in an airtight compartment called the thorax

59
Q

Where are the pleural membranes in the human breathing system

A

Lone the thorax and cover each lung

60
Q

What is the purpose of the pleural fluid in the human breathing system

A

Fluid between the membrane prevents friction between the lungs and chest cavity as the lungs move during ventilation

61
Q

Where is the diaphragm, what is it’s shape and what does it do?

A
  • The diaphragm is at the base of the thorax, a dome shaped sheet of muscle,
  • It separates he thorax from the abdomen
62
Q

Where are the ribs located in the human breathing system

A

They surround the thorax

63
Q

Where are the intercostal muscles located in the human breathing system

A

Between the ribs

64
Q

What is the trachea

A

A flexible airway that brings air into the lungs

65
Q

What are contained insides the lungs of a human.

A

Branching network of tubes called bronchioles which arise from bronchi

66
Q

What are at the ends of bronchioles?

A

Air sacs called alveoli

67
Q

Why are the cartilage rings around the trachea not complete at the back?

A

To allow the oesophagus behind it to bulge as the bolus of food is swallowed, without meeting a hard structure which would prevent the food from moving past

68
Q

How do mammals ventilate their lungs? What does this mean?

A
  • Negative pressure breathing

- Meaning for air to enter the lungs the pressure inside the lungs must be below atmospheric pressure

69
Q

Describe the stages of inspiration (inhalation)

A

A) external intercostal muscles contract
B) ribs are pulled upwards and outwards
C) at the same time the diaphragm muscles contract so it moves down and flattens
D) both actions increase thorax volume
E) this reduces pressure in the lungs
F) atmospheric pressure is now greater than the pressure in the lungs, so air is drawn into the lungs

70
Q

Describe the process of expiration (exhalation)

A

A) external intercostal muscles relax
B) ribs move downwards and inwards
C) at the same time the diaphragm muscles relax, so it domes upwards
D) both actions decrease the thorax volume
E) increases pressure in the lungs
F) air pressure in the lungs is now greater than atmospheric pressure so air is forced out of the lungs

71
Q

What is the main cause of air being forced out of the lungs during normal breathing?

A

The elastic recoil of the lungs, the lung tissue is elastic and regains it’s original shape when not being actively expanded

72
Q

What is the surfactant made of? Where is it located in the human breathing system?

A

-The surfactant is an anti sticking mixture made out of moist secretions containing phospholipids and protein inside the surfaces of the alveoli.

73
Q

What is the two main roles of the surfactant

A
  • It allows the gases to dissolve before diffusing in/out of alveoli
  • also has a low surface tension to prevent the alveoli collapsing during exhalation when air pressure is low
74
Q

Why is gas exchange in the alveolus very efficient? (5)

A
  1. Large surface area:volume ratio
  2. Gases dissolve In the surfactant moisture lining the alveoli
  3. Walls made up of squamous epithelium, only one cell thick :: short diffusion pathway
  4. Extensive capillary network surrounds the alveoli
  5. Capillary walls are also only one cell thick contributing to small diffusion pathway
75
Q

Why is the extensive capillary network surrounding the alveoli important

A

Vital for maintaining diffusion gradients as co2 is rapidly brought to the alveoli and oxygen is rapidly carried away

76
Q

Why is the diffusion pathway short in the alveolus?

A

Because BOTH the walls of the alveoli (made of squamous epithelium cells) and capillaries are only 1 cell thick

77
Q

Describe the gas exchange in the alveolus

A

1) deoxygenated blood enters the capillaries surrounding the alveoli
2)oxygen diffuses out of the air in the alveoli into the red blood cells in the capillary
3)carbon dioxide diffuses out of the plasma in the capillary into the air in the alveoli from where it is exhaled
(LOOK AT DIAGRAM ON PAGE 171)

78
Q

Name the compositions for the % oxygen in inspired vs expired air

Why does this occur?

A 
Inspired= 20%
Expired= 16%

Occurs because oxygen is absorbed into the blood at the alveoli and used in aerobic respiration

79
Q

What is the % composition of carbon dioxide in inspired vs expired air

What is the explanation for this?

A 
Inspired= 0.4%
Expired= 4%

This is because carbon dioxide is produced by respiration and dissolved from the plasma to the alveoli where it is expired

80
Q

What is the % composition of nitrogen in inspired vs expired air

What is the explanation for this?

A 
Inspired = 79% 
Expired = 79%

This is because nitrogen is neither absorbed nor used so all that is inhaled gets exhaled

81
Q

What is the % composition of water vapour in inspired vs expired air

What is the explanation for this?

A 
Inspired = variable 
Expired = saturated

This is because the water content of the atmosphere varies,
alveoli are permanently lined with moisture (surfactant) so water evaporates from them and is exhaled

82
Q

Why do insects face a risk of dehydration

A

Because like terrestrial organisms they live in arid habitats where water can evaporate from their body surface

83
Q

How do many terrestrial and insect organisms reduce water loss?
What is it made of?

A

Have a waterproof layer covering their body e.g the insect exoskeleton which is rigid and comprises of a thin wavy layer over a thick layer of chitin and protein

84
Q

How does gas exchange occur in insects?

A

Through paired holes called spiralled running along the side of the body

85
Q

What do the spiracles lead to in an insect?

A

Spiracles lead to a system of branched chitin lines air tubes called tracheae, which branch into smaller tubes called tracheoles

86
Q

Why is it beneficial to line the tracheole walls with chitin?

A

Chitin is impermeable to water so water can’t evaporate across tracheole walls

87
Q

How do spiracles reduce water loss?

A

Spiracles can open and close so gas exchange can take place and water loss can be reduced

88
Q

Why is it benefits for spiracles to have hairs?

A

Hairs covering spiracles contribute to water loss prevention and prevent solid particles getting in

89
Q

What gas exchange occurs in insects when resting

A

Diffusion through the spiracles where tracheae and tracheoles take in oxygen and remove carbon dioxide

90
Q

During periods of activity with a high metabolic rate what gas exchange do insects rely on?

A

Rely on movements of the abdomen to ventilate the tracheae

91
Q

Where does gas exchange take place in an insect?

A

The interface between tracheoles and muscle fibres

92
Q

Why is it important for the ends of the tracheoles to be fluid filled and close to muscle fibres?
What does this mean?

A

To allow oxygen to dissolve In the fluid and diffuse directly into the muscle cells (opposite for co2)
-this means no respiratory pigment or blood circulation is required

93
Q

LEARN DIAGRAM DOR TRACHEAL SYSTEM OF AN INSECT

A

LEARN DIAGRAM OF THE TRACGEOLE END INSIDE MUSCLE FIBRES

94
Q

What limitations does the insect not having a circulatory system cause

A

Diffusion is only efficient over small distances, limiting the size of the insect

95
Q

What gas exchange process do plants complete during the day?

A

Photosynthesis and respiration, as plant cells containing chloroplast have sunlight for photosynthesis

96
Q

Where does the co2 required for photosynthesis come from?

A

Some comes from the products of respiration but most diffuses into the leaves from the atmosphere

97
Q

What happens to the oxygen produced in photosynthesis

A

Some is used in respiration but most diffuses out of leaves

98
Q

What forms of gas exchange occurs in plants at night?

A

Plants only respire not photosynthesis

99
Q

How do plants gain oxygen for respiration at night

A

Some enters stem and roots by diffusion but most has exchange takes place at the leaves
LEARN DIGRAM ON PAGE 173

100
Q

What is the overall product produced by plants during the day?
Explain.

A

Oxygen
Because the rate of photosynthesis is faster than the rate of reaction :: more oxygen is produced in photosynthesis than is used in respiration

101
Q

What is the overall product produced by plants during the night?
Explain.

A

Carbon dioxide

At night photosynthesis doesn’t occur so no oxygen is produced

102
Q

Name the important structures in a leaf

A 
Cuticle 
Upper epidermis 
Palisade mesophyll cell
Spongy mesophyll 
Lower epidermis 
Sub stomatal air chamber 
Stoma 
Guard cell 
Cuticle 
LEARN DIAGRAM ON PAGE 173
103
Q

Why is the leafs diffusion pathway always short?

A

Because leaves are so thin

104
Q

How do the gases diffuse through the stomata

A

Down a concentration gradient into the sub stomatal air chambers where they diffuse through the intracellular spaces between the spongy mesophyll cells and into cells

105
Q

What maintains the diffusion gradients of oxygen/carbon dioxide between the inside and outside of a leaf?

A

Maintained by the mitochondria carrying out aerobic respiration and by chloroplasts carrying out photosynthesis

106
Q

Define the term cuticle

A

Each covering on a leaf secreated by epidermal cells which reduces water loss

107
Q

Why is the large surface area of a leaf vital for gas exchange and photosynthesis?

A

Gas exchange= room for many stomata

Photosynthesis= captures as much light as possible

108
Q

Why is the thinness of a leaf vital for gas exchange and photosynthesis?

A

Gas exchange= diffusion pathway for gases entering and leaving is short
Photosynthesis= light can penetrate through leaf

109
Q

Why is the air spaces In the spongy mesophyll vital for gas exchange and photosynthesis

A

Gas exchange= allows oxygen and carbon dioxide to diffuse between the stomata and the cells

Photosynthesis= allows carbon dioxide to diffuse to the photosynthesising cells

110
Q

Why are stomatal pores vital for gas exchange

A

They allow for gas exchange in and out of the leaf through opening and closing

111
Q

Name some more benefits for photosynthesis in a leaf

A
  • cuticle and epidermis are transparent allowing light to penetrate the the mesophyll
  • palisade cells are elongated to accommodate a large number
  • palisade cells are packed with chloroplasts to capture as much light as possible
  • chloroplasts rotate and move within mesophyll cells to be in the best positions for maximum light absorption
112
Q

Define the term stomata/stomatal pore

A

Pore on a lower leaf surface, and other aerial parts of a plant, bounded by 2 guard cells, through which gases and water vapour diffuse

113
Q

Describe guard cells

A

Only Epidermal cells with chloroplasts, also have unevenly thickened walls

114
Q

Briefly describe thickness of stomatal cell wall

A

The inner cell wall next to the stomatal pore is thicker than the outer wall

115
Q

Describe the mechanism In the stomata during the day

A
  • if water enters the guard cells they become turgid and swell and the pores open
  • if water leaves the guard cells they become flaccid and the pores close
116
Q

Describe the steps that causes the stomatal pore to open (5)

A
  • chloroplasts In guard cells photosynthesise producing ATP
  • ATP provided energy for active transport of K+ ions into guard cells from surrounding epidermal cells
  • stored starch (in starch grains) is converted to Malate
  • stored K+ and malate ions lower water potential in guard cells making it more negative
  • water enters by osmosis
  • guard cells expand as the absorb water but less so in areas where the cell wall is thick causing guard cells to stretch and a pore appears
117
Q

What is transpiration

A

A process where plants lose water by evaporation through their stomata

118
Q

What happens if plants loose too much water?

A

They wilt

119
Q

Why are stomatal pores positioned on the lower side of the leaf?

A

Because sunlight on the upper surface of the leaf would increase evaporation; so stomata on the lower minimises water loss

120
Q

What other aspect of a leaf reduces water loss?

A

The waxy cuticle on the upper surface

121
Q

When do stomatal pores close and why

A
  • at night to prevent water loss when there is insufficient light for photosynthesis
  • in very bright light, as this is generally accompanied by intense heat which would increase evaporation
  • if there is excessive water loss
122
Q

Why does only some of the air breathed in reach the gas exchange surface?

A
  • air in the alveolus is stationary
  • not all air inhaled passes out in the next expiration
  • the inspired air has to change places with the alveolar air

✅Biology AS Unit 2 (5 decks)

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